Advances in molecular biology have allowed the development of biological agents useful in modulating protein or nucleic acid activity or expression, respectively. Many of these advances are based on identifying the primary sequence of the molecule to be modulated. For example, determining the nucleic acid sequence of DNA or RNA allows the development of antisense or ribozyme molecules. Similarly, identifying the primary sequence allows for the identification of sequences that may be useful in creating monoclonal antibodies. However, often the primary sequence of a protein is insufficient to develop therapeutic or diagnostic molecules due to the secondary, tertiary or quartenary structure of the protein from which the primary sequence is obtained. The process of designing potent and specific inhibitors or activators has improved with the arrival of techniques for determining the three-dimensional structure of an enzyme or polypeptide to be modulated.
The phenylpropanoid synthetic pathway in plants produces a class of compounds know as anthocyanins, which are used for a variety of applications. Anthocyanins are involved in pigmentation and protection against UV photodamage, synthesis of anti-microbial phytoalexins, and are flavonoid inducers of Rhizobium modulation genes 1–4. As medicinal natural products, the phenylpropanoids exhibit cancer chemopreventive activity, as well as anti-mitotic, estrogenic, anti-malarial, anti-oxidant, and antiasthmatic activities. The benefits of consuming red wine, which contains significant amounts of 3,4′,5-trihydroxystilbene (resveratrol) and other phenylpropanoids, highlight the dietary importance of these compounds. Chalcone synthase (CHS), a polyketide synthase, plays an essential role in the biosynthesis of plant phenylpropanoids.
An improvement in the understanding of the structure/function of these enzymes would allow for the exploitation of the synthetic capabilities of known enzymes for production of useful new chemical compounds, or allow for the creation of novel non-native enzymes having new synthetic capabilities. A need exists, therefore, for a detailed understanding of the molecular basis of the chemical reactions involved in polyketide synthesis. The present invention addresses this and related needs.